Canal boat design

Didn't watch the video but I think it's used in hotels and similar. Saves having a very long cold leg if nobody else has taken hot water recently.

I think you need a well insulated pipe run, otherwise you're losing heat by circulating it around. You may also need to make sure temperature at the end of the run is >60C even in the worst case conditions, otherwise it could be a breeding ground for legionella.

(not sure if this is a reason for the 'caution scalding hot water' often seen in commercial premises)

It may not make sense if the hot water demands are infrequent - in a hotel you know somebody is going to be opening a tap on average every 5 minutes or whatever, whereas a house can go hours with no taps being opened at which point all the heat is being wasted.

THeo

It is common in larger commercial premises and hotels etc. Also sometimes found in (typically larger) houses. Probably less common in smaller places.

Usually called a secondary circulation system/loop, or hot water loop. Some boiler control systems have capabilities to include timed operation of circulation pumps. (so you may opt to only run it at times you expect frequent hot water use). I note its one of the many controls available on my Vaillant controller. (although I install the whole system myself, I did not bother with a circulation loop, since all the bathrooms are clustered around the hot water cylinder anyway - so the only slightly longer pipe run it to the hot taps in the kitchen).

From a user's point of view the main pro is instant hot water at any tap, so no running off litres of water waiting for hot water. The main con would be slightly increased energy use to run the system and higher installation costs.

Worth noting that it generally is only an option with stored hot water systems, so the many properties using combi boilers will be precluded from using it, unless they also include some additional hot water storage facility.

You need a very well lagged hot water pipe setup, and also need additional pipe for the return connection(s).

I moved the boiler and DHW cylinder into the garage of my previous house and, because the pipe run was then fairly long, formed a loop and put a DHW circulation pump on a timer and pipestat. The upside is minimal delay for hot water, the downside is a loss of stratification in the cylinder. When I replaced the heating and other plumbing in this house I put the boiler and cylinder in what was the coal store and then put a pumped DHW loop to reduce the hot water delay to the taps. All of the bedrooms have basins and the furthest is quite a way from the cylinder as the pipe flies, so to speak - a similar situation to that on a narrow boat

The circulation pump on the smaller installs such as big houses that I have wired up are usually put on a timer.

Our basic Grundfos recirc pump is on a timer. They also do a smart version which learns the timing of demand and turns itself on in anticipation.

See "grundfos comfort autoadapt"

How incorrect would it be to say "that is cool"?

Thank you